Download Management Guidelines for the Protection of Heronries in Ontario

MANAGEMENT GUIDELINES FOR THE PROTECTION
OF HERONRIES IN ONTARIO
ONTARIO MINISTRY OF NATURAL RESOURCES
Prepared by Irene Bowman
and Joanne Siderius
MNR # 51610
ISBN 0-7794-2363-1 (Internet)
April 1984
2
Table of Contents
Page
1.0
Introduction.........................................................................................................................4
1.1
Herons and Egrets in Ontario.............................................................................................4
1.2
Response to Disturbance......................................................................................................7
1.2.1
Abandonment of the Colony or Individual Nests...................................................8
1.2.2
Increased Predation on Eggs and Young .................................................................8
1.2.3
Mortality Due to Exposure ........................................................................................8
1.2.4
Loss of Food.................................................................................................................8
1.2.5
Mortality Resulting from Alarming Young............................................................8
2.0
Management Objectives.......................................................................................................9
3.0
Management Guidelines.....................................................................................................9
3.1
Inventory of Heronries.........................................................................................................9
3.1.1
Ontario Heronry Inventory ......................................................................................9
3.1.2
Ministry Reports of Heronries ...............................................................................10
3.1.3
Encouragement of Site Reporting..........................................................................10
3.1.4
Confidentiality of Colony Locations.....................................................................10
3.2
Protection/Management Relative to Size of a Heronry and Other Factors......................11
3.3
Habitat Conservation for Heronries..................................................................................11
3.3.1
Inform Property Owners or Developers ................................................................11
3.3.2
Provide Input Early ..................................................................................................11
3.4
Buffer Zones .....................................................................................................................12
3.4.1
3.4.1.1
3.4.1.2
3.4.2
Heavy Development Buffer Zone ...........................................................................13
Size.......................................................................................................................... 13
Prohibited Activities................................................................................................ 13
Minimum Buffer Zone ...........................................................................................15
3.4.2.1
Size.......................................................................................................................... 15
3.4.2.2
Specifications for Entry................................................................................................. 15
3.4.2.3
Activities Prohibited in Minimum Buffer Zone at All Times............................................... 15
3.4.2.4
Activities Prohibited in Minimum Buffer Zone During Breeding Season ............................... 15
3.4.2.5
Activities Permitted in Minimum Buffer Zone and Colony ................................................. 16
During Non-nesting Season........................................................................................................... 16
3.4.3
3.5
Aquatic Buffer Zone ................................................................................................16
Habitat Management.........................................................................................................17
3.5.1
Feasibility .................................................................................................................17
3.5.2
When to be Undertaken..........................................................................................17
3
3.5.3
Management of Colony Site and Buffer Zone......................................................17
3.5.3.1
3.5.3.2
3.5.3.3
3.5.3.4
3.5.3.5
3.6
Techniques Not to be Used........................................................................................... 17
Suggested Techniques.................................................................................................. 17
Management of Feeding Areas ....................................................................................... 21
Fencing or Posting of Colonies...................................................................................... 21
Protection of Sites Associated with Heronries ................................................................... 21
Research in Colonies.........................................................................................................21
3.6.1
Conditions of Approval for Research Proposals...................................................21
3.6.2
Use of Standard Survey and Census Techniques .................................................22
3.6.3
Aerial Surveys and Censuses.................................................................................22
3.6.4
Guidelines for Persons Entering Heronries.........................................................23
3.7
Education and Interpretation ...........................................................................................25
3.7.1
Messages ...................................................................................................................25
3.7.2
Interpretive Tools.....................................................................................................25
3.7.2.1
3.7.2.2
3.7.2.3
3.7.2.4
3.7.2.5
3.7.2.6
Signs.................................................................................................................... 25
Pamphlets.................................................................................................................. 26
News Releases and Advertisements................................................................................. 26
Educational Viewing Programs..................................................................................... 26
A/V Shows and Exhibits.............................................................................................. 27
Local Interest Groups................................................................................................... 27
4.0
Appendices.........................................................................................................................27
4.1
Census Instructions for Heronries.....................................................................................27
4.1.1
Terms Defining Status of Nests..............................................................................27
4.1.2
Censusing of Great Blue Heron Colonies in Woodlots and Swamps ...............28
4.1.3
Great Blue Heron Colonies in Deep Beaver Ponds.............................................28
4.1.4
Colonies With Species Nesting Close to Ground................................................29
4.2
Ontario Heronry Inventory Census Field Sheets and Record Sheets...............................30
4.3
Forest Management Plans.................................................................................................34
4.4
Buffer Zones Recommended by Colonial Bird Authorities .............................................35
5.0
Selected References............................................................................................................36
List of Figures
Figure 1:
Figure 2
Figure 3
Figure 4
Page
Nesting Distribution of Colonial Herons in Ontario as of 1981 ...................................................... 6
Recommended Buffer Zone.................................................................................................... 14
Sensitive Periods in the Nesting Cycle of Great Blue Herons....................................................... 19
Sensitive Periods in the Nesting Cycle of Black-crowned Night Herons......................................... 20
4
MANAGEMENT GUIDELINES FOR THE PROTECTION
OF HERONRIES IN ONTARIO
1.0
Introduction
The maintenance of established heronries and associated feeding areas is essential to
ensure the stability of breeding populations of herons and egrets (Family: Ardeidae).
These colonial nesters are especially vulnerable to human disturbance and habitat
destruction during the breeding season when large numbers of birds are concentrated in
a relatively confined area. Colonial birds tend to desert nests and entire colonies if
disturbed during the periods of pair-formation, nest construction or early egg laying
(Blaker, 1969; Jenni, 1969; Buckley and Buckley, 1978; Tremblay and Ellison, 1980).
Established heronries, and in particular large established heronries consisting of
hundreds of nesting pairs, are a valuable biological resource. They may be occupied
for decades or even centuries because of habitat conditions that are conducive to
reproductive success (Bent, 1963; Hagey, n.d.). If forced to relocate, alternative
habitats may be of a poorer quality (Vermeer, pers. comm., 1978). Other
consequences of disturbance include fragmentation of breeding populations, total
reproductive failure in colonies that have relocated, or reduced numbers of nesting
pairs and reduced reproductive output per pair in relocated colonies (Buckley and
Buckley, 1978). Desertion of large colonies that are responsible for the major portion
of a population's reproductive output can affect the stability of the entire regional
population of herons, even if the desertion is followed by relocation.
1.1
Herons and Egrets in Ontario
The following communally nesting heron or egret species have been recorded as
breeding in Ontario: great blue heron (Ardea herodias), black-crowned night heron
(Nycticorax nycticorax), green-backed heron (Butorides striatus), great egret
(Casmerodius albus), and cattle egret (Bubulcus ibis). Green-backed herons usually
nest singly, but are included here because they sometimes occur in small colonies of
ten or fewer nests (ONRS*). The guidelines apply to green backed herons only when
they are present in colonies.
In Ontario, large mixed-species heronries are found mainly in the extreme
southwestern corner of the province where the breeding ranges of all five species
mentioned above coincide. Black-crowned night herons, cattle egrets, and great egrets
usually nest in colonies containing other heron species.
__________
*Ontario Nest Record Scheme
5
Cattle egrets have not been reported as nesting in Ontario since 1978 (ONRS) but
since this species is at the edge of its range (Fig. 1), it could presumably nest here
again. Cattle egrets have been reported nesting in mixed-species heronries situated on
some islands in the western arm of Lake Erie, and have nested as far north as
Wellington County. Great egrets have been reported nesting in western Lake Erie and
also on the mainland south of Amherstburg.
The black-crowned night heron is the second most numerous colonially nesting heron
species in Ontario, and breeds along the shores of the Great Lakes eastward to
Northumberland and Frontenac Counties (ONRS), and as far north as Manitoulin
District.
The great blue heron is the most numerous and widely distributed heron in Ontario
(Dunn et al., 1981) breeding as far north as latitude 54o12' (Gray, 1978) (Fig. 1). Data
from a two-year (2) census, conducted in 1980 and 1981 as part of the Ontario
Heronry Inventory (OHI), gave a conservative estimate of 13,022 breeding pairs of
great blue herons in Ontario (Dunn et al., 1981). The Ontario population appeared to
be larger and denser than populations censused in other inland areas (Dunn et al.,
1981). Great blue heron colonies located on the Canadian Shield in Ontario (eg., those
colonies north of latitude 45oN, approximately) are smaller and more numerous than
colonies south of the Shield (Dunn et al., 1981). It also appears that a large
proportion of the province's breeding pairs of great blue herons are concentrated in
relatively few colonies located in the Ontario Heronry Inventory's Southern Sample
Area: "The herons nesting in the Southern Sample Area which made up an estimated
24% of the province's total are more vulnerable than elsewhere as a result of being
concentrated into larger and more dispersed colonies" (Dunn et al., 1981).
6
Figure 1: Nesting Distribution of Colonial Herons in Ontario as of 1981
(Great Blue Heron, Black-crowned Night Heron, Great Egret, Cattle Egret+ and Green-backed
Heron) (from ONRS, OHI# and Godfrey, 1966).
_______
*indicates past nesting localities
+
not known to have nested in Ontario since 1978.
#
Ontario Heronry Inventory
7
1.2
Response to Disturbance
Herons of all species are unpredictable in their response to the disruption of a colony.
The severity of the response does not always correspond to the magnitude of the
disturbance, since even seemingly "innocuous" activities can produce serious results.
The effects of human disturbance very in response to a number of factors, including
stage of the nesting cycle, degree of habituation to disturbance, size of the colony,
species of heron present, type of habitat surrounding the colony, region within the
species' range, and the nature of the disturbance. Perhaps the most important factors
to be considered are the timing of the disturbance in relation to critical periods of the
nesting season, and the degree to which the birds are able to adjust to human activities
in or near nesting areas.
Heronries are frequently situated in areas isolated from human disturbance, for
example, in swamps, marshes or beaver ponds, in woodlots adjacent to water bodies,
or on islands (Adams et al., 1973; OHI). Herons have, in rare instances, tolerated
human settlement and activities near their breeding areas; some herons have even
selected colony locations near areas of human disturbance (Kelsall, pers. comm.;
OHI), presumably because of excellent feeding opportunities. However, disturbances
cannot be imposed arbitrarily on any heronry. Herons inhabiting remote island or
woodland locations that have experienced few past disturbances are unlikely to
tolerate human activities near their colonies. Some colonies have been deserted or
relocated after the destruction or alteration of their habitat during the non-nesting
season (Bjorklund, 1975).
Birds nesting in large colonies and those accustomed to a certain amount of
disturbance are less likely to desert the colony, although some nests may be deserted
(Bjorklund, 1975; Werschkul et al., 1976, Kelsall, pers. comm.), and nestings may be
delayed.
The density of vegetation in and surrounding the colony may also influence the
impact of disturbance. Removal of trees or shrubbery in or near a colony would
facilitate intrusion by humans or predators, and in some instances would result in
fluctuating water levels in the colony. The exposure of an increased number of nests
would also be undesirable. Maintenance of trees and shrubs around the colony, on the
other hand, would provide a buffer against disturbance and provide alternate nest
sites.
The frequency of colony relocation is influenced by geographic location. Colonies in
northern Ontario, for example, are smaller and more numerous than more southerly
colonies (Dunn et al., 1981), and appear to change location more frequently (OHI).
8
As a rule, disturbances in colonies initiate instabilities that can lead to loss of habitat
and/or decreased reproduction. Some of the major disturbance-related factors that
have a negative impact on reproduction are as follows:
1.2.1
Abandonment of the Colony or Individual Nests
Abandonment is most likely to occur in the pre-nesting (courtship) period
and up to hatching time. Adult herons do not develop a strong attachment
to the nest until young are present (Adams et al., 1973).
1.2.2
Increased Predation on Eggs and Young
Disturbances causing even the temporary absence of adults from the nest
may result in a significant increase in predation on eggs and young (Bent,
1963; Teal, 1965; Wolford, 1966; Wolford and Boag, 1971). Predators
such as crows, ravens, gulls and racoons may become accustomed to this
source of food if adults are often kept from the nest (Simpson and Kelsall,
1978).
1.2.3
Mortality Due to Exposure
Disturbances which prevent adults from attending the nest contribute to
mortality of embryos and young due to exposure (Teal, 1965; Wolford,
1966; Pratt, 1970; Adams et al., 1973; Tremblay and Ellison, 1976).
1.2.4
Loss of Food
Disturbances cause interruptions in the feeding routine, which result in the
loss of food by the young. In addition, the young tend to regurgitate meals
when frightened (Cottrille and Cottrille, 1958; Bent, 1963; Teal, 1965;
McVaugh, 1972).
1.2.5
Mortality Resulting from Alarming Young
Alarming older young causes them to leave the nest and many fall to their
deaths or become entangled in branches while scrambling through the
vegetation (Bent, 1963; Teal, 1965; Wolford, 1966, Wiese and SmithKenneally, 1977). Young that stray from their own nests may also be
attacked by other herons whose territories they may venture into (Blaker,
1969). In addition, adults do not normally feed young that have fallen to
the ground.
9
2.0
Management Objectives
2.1
To prevent the loss of colonial nesting sites, feeding areas and any other sites
important to the reproductive success of herons and egrets in Ontario.
2.2
To provide information that will enable the Ministry of Natural Resources, as
well as other ministries, agencies, developers, landowners, naturalists and
recreationalists to minimize disturbances to heronries and to recognize the habitat and
breeding requirements of herons.
2.3
To encourage continuing cooperation between the Ontario Ministry of Natural
Resources, the Canadian Wildlife Service, scientific researchers and naturalists, in
order to maintain current information on the status of Ontario's heron populations,
and to use that information as a basis for protecting colonies and making appropriate
management decisions.
2.4
To emphasize the need for land use plans that protect heronries by recognizing
the habitat/breeding requirements of herons.
2.5
To encourage educational programs to promote the appreciation of herons and
to inform the general public, especially landowners and recreationalists, about the
sensitivity of herons to disturbance.
3.0
Management Guidelines
3.1
Inventory of Heronries
3.1.1
Ontario Heronry Inventory
The Ontario Heronry Inventory (a project supported by the Ministry of
Natural Resources, the Canadian Wildlife Service and Long Point Bird
Observatory) maintains an inventory of heronry sites; copies of the
inventory are located at main office, in the Wildlife Branch, and in Regional
Offices of the Ministry. Information is contributed by Ministry
personnel, federal and municipal government staff, naturalists,
recreationalists, private landowners, and other members of the public.
Information recorded for each colony includes: location, size and
ownership of the colony site, and a description of the habitat. Information
from a 1980 and 1981 Ontario-wide census of great blue heron colonies is
included in the inventory.
10
3.1.2
Ministry Reports of Heronries
The locations of heronries reported by Ministry staff have been mapped
and indexed by the Wildlife Branch. Sites are marked on 1:50,000 and
1:250,000 topographical maps and a cross-referenced card index of
colonies is maintained for each map scale. Available information on
numbers of nests in colonies, egg laying and hatching dates is recorded on
the 1:50,000 scale index cards.
Records of new sites and updated information on previously mapped sites
are to be reported to head office by district staff.
If colonies are censused, the guidelines in Section 3.6.4 are to be followed
to prevent disturbances. Ground censuses are to follow the methodology
outlined in Appendix 4.1, Census Instructions for Heronries. All census
results should be recorded on the field sheet and summarized on the record
sheet. Sample sheets are included in Appendix 4.2. Site locations are to be
mapped on 1:50,000 maps.
One copy of the census record sheet and the map for each site should be
kept by the district. Data on the census report forms should be
summarized by the district and forwarded to the region.
3.1.3
Encouragement of Site Reporting
District field staff should encourage landowners, naturalists, hunters,
trappers, fishermen, and recreationalists to notify the Ministry of Natural
Resources about the locations of heronries they may know of. Educational
or interpretive materials could be used to inform members of the public
about the value of heronries, their vulnerability to disturbance and to
encourage people to report any colonies encountered (Sec. 3.7).
3.1.4
Confidentiality of Colony Locations
Information on colony locations should have a restricted distribution.
Research proposals requesting information on colony locations should be
reviewed by Ministry biologists (Section 3.6). Researchers whose
proposals are approved should understand that the information on colony
locations is given in confidence and is not to be circulated.
11
3.2
Protection/Management Relative to Size of a Heronry and Other Factors
All colonies which contribute significantly to regional populations of heron species
should be given full protection, and managed, if necessary, to ensure their continuance,
and to minimize disturbances.
Larger, denser colonies tend to supply more young to the population than do smaller,
less dense colonies. Dunn et al (1981) found 44 colonies with more than 50 active
nests in Ontario, and these colonies contained 37% of the province's total estimated
population of great blue herons.
A colony of any size isolated by a large radius from other colonies should be afforded
protection. The colony may occupy the only suitable breeding habitat in the area, and
may represent the only source of breeding birds within the area.
The size of a colony, however, is not the only factor that should be looked at in
evaluating its regional significance. In northern Ontario, virtually all great blue heron
colonies are small in size because of marginal habitat conditions. The significance of
these colonies should, therefore, not be assessed by making comparisons with much
larger colonies found in southern Ontario.
3.3
Habitat Conservation for Heronries
The habitat requirements of herons require consideration in land-use planning, and
when considering proposals concerning development, resource use, and the
recreational use of Crown lands. The following initiatives on the part of fish and
wildlife managers will help to ensure protection and conservation of this valuable
wildlife resource.
3.3.1
Inform Property Owners or Developers
An effort should be made to inform the landowner about the special
requirements of heron species as soon as the location of a heronry on
private land is known. Contact should be made with any public or private
agency involved in a proposed development before the activity threatens
an existing heronry.
3.3.2
Provide Input Early
Fish and wildlife managers should be aware of the appropriate time for
providing input into resource use plans that could threaten heronries.
Habitat concerns should be identified during the early stages of this
process, since they are much more likely to receive serious consideration if
12
identified before detailed resource-use plans are developed. In the case of
major activities or developments proposed for previously unsurveyed
areas,* provisions should be made to protect heronries that are discovered
during inventories.
It is not possible to discus in detail the steps for each type of development
which could threaten a heronry. However, the development of forest
management plans, and a discussion at the appropriate time for providing
input, is included in Appendix 4.3.
3.4
Buffer Zones
Written specifications for the establishment of buffer zones shielding heronries from
habitat destruction or disturbance should be required in all permits for activities or
developments that pose a potential threat to those heronries.
Buffer zones should be established around each active heronry that is vulnerable to
human disturbances during the sensitive breeding season. This season is roughly as
follows in the sections of the province indicated:
Southern Ontario
Central & Northern Ontario
(lat.42oN - 44oN)
(lat.44o01' - 54oN)
March 15 - August 1
April 1 - August 15
Arrival dates in the province and the timing of egg laying can vary greatly, according
to latitude. Werschkul et al. (1977) noted that larger heronries tended to have earlier
arrival dates on the Oregon coast.
In view of the varying sensitivity of herons in different colonies, it is not possible to
set a precise distance that will serve as a buffer zone in all cases. Response to
disturbance varies with factors already discussed, including geographical location,
degree of habituation to disturbance, size of colony, species present, and so on. As a
general rule, it should be remembered that the majority of herons are extremely
sensitive to disturbance, and that the widest buffer zone possible should be
established around colonies.
For the purposes of these guidelines, the following zones represent the minimum level
of protection that should be provided for heronries. Information on the buffering
distances recommended by various colonial bird authorities is provided in Appendix
4.4
_______
*Environmental impact studies would be required under the Environmental Assessment Act for
most major developments (subdivisions excepted).
13
3.4.1
Heavy Development Buffer Zone
3.4.1.1
Size
During the sensitive breeding season, a heavy development
buffer zone of one (1) kilometre should be established,
extending from the peripheral nests of the colony.
3.4.1.2
Prohibited Activities
Activities having a high disturbance factor, such as road
construction, logging, forest site-preparation, pipeline
construction, blasting and dredging should be prohibited in the
heavy development buffer zone during the nesting season.
14
Figure 2 Recommended Buffer Zone
15
3.4.2
Minimum Buffer Zone
3.4.2.1
Size
During the sensitive breeding season, a minimum buffer zone of
300 metres (1000 feet) should be established, extending from
the peripheral nests of the colony (Fig. 2).
3.4.2.2
Specifications for Entry
The minimum buffer zone and colony proper should be entered
during the least sensitive parts of the breeding season (Figs. 3
and 4), and only by the following:
3.4.2.3
i
Staff of the Ontario Ministry of Natural Resources
or Canadian Wildlife Service who are conducting the
yearly census, or other studies;
ii
Persons conducting research approved by the
Ontario Ministry of Natural Resources (see Section
3.6.1).
Activities Prohibited in Minimum Buffer Zone at All Times
Activities that would necessitate the removal or disturbance of
trees or ground vegetation in the minimum buffer zone and in
the colony proper should be prohibited at all times. The
vegetation should remain intact to serve as a deterrent to man
and predators (see Section 3.6.3). Trees in the buffer zone are
also needed as nesting sites, should the colony increase in size,
and to shield existing nests from the elements.
The use of all-terrain vehicles and snowmobiles is prohibited
since these activities create trails through the vegetation making
access to the colony easier, and they may also initiate erosion.
3.4.2.4
Activities Prohibited in Minimum Buffer Zone During Breeding
Season
All of the following activities or types of intrusion should be
prohibited in the minimum buffer zone and colony proper
during the sensitive breeding season:
16
3.4.2.5
i
Pedestrian foot traffic.
ii
Off-road vehicles (all-terrain vehicles, swamp
buggies, trail bikes, etc.).
iii
Recreational activities, including camping, hunting,
bird watching, and photography.
iv
Pets or livestock.
v
All development, forest management and wildlife
habitat management activities.
Activities Permitted in Minimum Buffer Zone and Colony
During Non-nesting Season
Activities that could be permitted (unless otherwise prohibited)
in the minimum buffer zone and colony proper during the nonnesting season are as follows:
3.4.3
i
Habitat management to enhance the colony site.
ii
Wildlife management activities that do not interfere
with the nesting habitat (eg., erecting wood duck boxes
in areas outside of colony proper).
iii
Recreational activities such as hiking, camping, and
hunting.
Aquatic Buffer Zone
During the sensitive breeding season, an aquatic buffer zone of at least 300
metres (1000 feet) should be established to protect heronries situated on
the shores of islands, lakes or rivers. If posting of the aquatic buffer is not
possible, landing on the shore near the colony should be prohibited.
In the case of heronries situated on water bodies which are being opened
up to boat traffic, it may be advisable to post signs in the water notifying
recreationalists of the establishment of aquatic buffer zones.
17
3.5
Habitat Management
3.5.1
Feasibility
The feasibility of undertaking habitat management in any colony should be
carefully examined. Management may be desirable in some cases to
maintain the vegetation in the colony proper and minimum buffer zone, or
to improve the quality of aquatic feeding areas. Since factors influencing
nest site selection are poorly understood, the habitat must not be altered in
ways that could result in rejection of the site by the birds.
For most Ontario heronries, the major management requirement is colony
protection. Habitat acquisition should be considered in order to provide
long-term protection for important colonies.
3.5.2
When to be Undertaken
Habitat management should be undertaken in the colony proper and
minimum buffer zone only in the non-breeding season (eg., the period
following the dispersal of the birds from the heronry and surrounding area,
and ending before the arrival of the adults in spring. (see Figs. 3 and 4).
3.5.3
Management of Colony Site and Buffer Zone
3.5.3.1
Techniques Not to be Used
No trees or shrubs, living or dead, should be removed from the
colony proper or from the minimum buffer zone of the colony.
3.5.3.2
Suggested Techniques
The following management techniques could be useful, if
improvement of habitat is desirable:
i
Manage for dense ground vegetation, which helps to
shield colonies from human intrusions and ground
predator disturbance. Install artificial nest baskets
(Markham and Brechtel, 1978) to replace nesting sites
that have been lost. This effort should be coupled with
long-term management for preferred nesting trees and
shrubs. Artificial nests may keep colonies active, but
cannot be relied upon to maintain populations.
18
ii
Obtain help from a plant pathologist to determine if
diseased nesting trees in a colony can be saved.
iii
Manage for tree or shrub species preferred as nesting
sites.
iv
Manipulate water levels through cooperation with the
appropriate water-control agencies, to prevent
inundation of the floor of the colony. Flooding could
result in the death of trees or ground cover.
19
Figure 3 Sensitive Periods in the Nesting Cycle of Great Blue Herons
20
Figure 4 Sensitive Periods in the Nesting Cycle of Black-crowned Night Herons
21
3.5.3.3
Management of Feeding Areas
Cooperation with water-control agencies may be necessary to
maintain water quality, levels, and flow at key heron feeding
areas, thereby ensuring optimum production of prey species.
3.5.3.4
Fencing or Posting of Colonies
Fencing or posting may not be required or even desirable in
colonies that are not subject to disturbance, or in which ground
vegetation is dense enough to discourage visitors, since signs
and fences may focus attention on that colony.
Buckley and Buckley (1978) recommend posting of all colonies
vulnerable to human disturbances with educational/admonitory
signs. If greater protection is required, they recommend
"symbolic" twine fencing, but never wire.
3.5.3.5
Protection of Sites Associated with Heronries
In addition to the colony site, a number of other sites used by
herons and egrets during the breeding season may require
special protection - for example, feeding and loafing areas.
These "associated" sites have not been identified for the
majority of heronries. However, if an important site is known,
the level of protection to be provided should be decided by the
district concerned.
3.6
Research in Colonies
3.6.1
Conditions of Approval for Research Proposals
3.6.1.1
All research proposals for work in heronries will be reviewed
and evaluated by the Wildlife Branch. Proposals should be
rejected:
i
if the birds would be severely disturbed because of the
nature of the research;
ii
if disturbances would be caused in the sensitive periods
of the breeding season (Figs. 3 and 4);
22
iii
3.6.1.2
if there is evidence that precautions to avoid
disturbances are inadequate.
Persons in charge of approved work in colonies will be
responsible for the actions of members of their work teams.
Persons conducting approved work in colonies will be asked to
assess and recommend ways to minimize disturbances caused
by their visits.
3.6.1.3
3.6.2
The Ministry shall release colony locations to legitimate
researchers on the condition that such information is treated
confidentially.
Use of Standard Survey and Census Techniques
Where applicable, standard survey and census techniques and terminology
(Appendices 4.1 and 4.2) should be used by researchers and by Ministry
workers, so that present and future status and long-term trends of heron
populations will be comparable within Ontario.
3.6.3
Aerial Surveys and Censuses
Aerial surveys and censuses of heronries can frequently be combined with
other work in the districts. Although aerial censuses are not as accurate as
ground censuses, they are an effective means of monitoring colonies over a
wide area. If more accurate data are needed, ground censuses should be
conducted.
Kushlan (1979) suggests the following precautions to minimize colony
disturbance when censusing from the air:
The colony should be approached gradually by first circling it at a distance
either latitudinally or horizontally, and then moving closer for the count.
The aircraft should fly around the periphery of the colony. Helicopters
should fly slowly but not hover over the colony. Continual attention
should be paid to signs of drastic disturbance during the census.
Aerial census should not be conducted during the most sensitive stages of
the nesting season (Figs. 3 and 4).
23
3.6.4
Guidelines for Persons Entering Heronries
Extreme caution must be exercised in entering an occupied heronry.
Persons entering heronries during the breeding season for research or for
other approved activities will avoid all undue disturbances to both adult
birds and young by following these guidelines:
3.6.4.1
Heronries should not be entered during the periods of
courtship, pair formation, nest building or egg laying, because
of the danger of nest or colony abandonment.
3.6.4.2
Heronries should not be entered while the adults are incubating
eggs or brooding young because embryos and young can die as a
result of exposure or predation while adults are absent from the
nest.
3.6.4.3
Heronries should not be entered while the unfledged young are
capable of scrambling from the nest. Young may become lost,
or fall to the ground in an attempt to escape observers.
3.6.4.4
Heronries should not be entered on very hot or very cold days,
or during rain, to avoid unnecessary exposure of the young to
inclement weather conditions.
3.6.4.5
When research is planned in a colony, the sequence of
courtship and incubating behaviour should be observed from a
distance in order to determine the best time to enter the colony.
An effort should be made to obtain the advice of experts
involved in colonial bird research before colonies are entered.
Figures 3 and 4 depict sensitive times of the breeding season
(eg., courtship, nesting building, egg laying, incubation,
brooding and presence of older young) for great blue herons and
black-crowned night herons.
3.6.4.6
The routine to be followed in the heronry should be established
well in advance to minimize the duration of the disturbance.
The layout of the colony should be determined before entry
(from air photos) to allow the organized movement of
researchers.
Heronries should be entered slowly, by one researcher, or by a
very small number of researchers, to avoid alarming the birds.
Observer teams should not split up over a wide area once inside
24
the colony. The same route should be followed when entering
or leaving the colony. All movements should appear unhurried
and there should be a minimum of conversation. No attempt
should be made to hide since "the sudden appearance of anyone
invariably creates panic.Ó (McVaugh, 1972).
3.6.4.7
Heronries should be entered approximately three hours after
the early morning or late afternoon feedings to minimize
regurgitation of food by the young. Entry time in a particular
colony should be determined by observing the feeding routine
at a distance.
3.6.4.8
Only one visit should be made per heronry in the least sensitive
period of the nesting season, and no visits should take place
during the sensitive times (Figs. 3 and 4). If additional trips are
absolutely necessary, they should be infrequent and of short
duration to minimize predation while adults are absent from the
nest, and to prevent predators from following scent trails into
the colony.
3.6.4.9
If extended studies are to be conducted, heronries should be
entered over a period of hours, or days if possible, to accustom
the birds to the presence of humans (McVaugh, 1972).
3.6.4.10
If heronries are entered while the young are too small to defend
themselves against avian predators, special care must be taken
to avoid times when large numbers of crows, ravens or gulls are
in the vicinity.
3.6.4.11
If crows, ravens, gulls or other predators begin to enter a
colony when researchers are present, the researchers should
leave immediately.
3.6.4.12
If young do leave the nest, no attempt should be made to
replace them. Eggs and young must not be touched or
disturbed in any way. Buckley and Buckley (1978) include
these actions and also the chasing of young (eg., to count them)
under the title ÒProhibited BehaviourÓ.
3.6.4.13
No person conducting research in a heronry, nor any person
entering or working in the buffer zone shall construct a foot trail,
snowmobile trail, or other access route that will facilitate
accessibility to a heronry or increase its vulnerability in any way.
25
3.7
Education and Interpretation
An effective education strategy aimed at informing people about colonial birds and
their special requirements is essential to ensure the protection of Ontario's heronries.
"Much of the enforcement called for now could be discarded if the human users of
these areas were educated to the needs and sensitivities of the animals." (Buckley and
Buckley, 1978)
3.7.1
Messages
The following messages should be incorporated in all interpretive materials
or programs:
3.7.2
1)
Heronries should not be disturbed.
2)
Heronries on private and public lands should be conserved.
3)
Locations of any heronries found should be reported to the
Ministry of Natural Resources. (Locations should not, however,
be published in educational or interpretive materials made available
to the general public.)
Interpretive Tools
The interpretive tools described in this section are suggested as examples
only of materials or program activities that might be implemented to
promote the messages outlined above.
3.7.2.1
Signs
The benefits of posting educational or warning signs must be
weighed against the disadvantages. Signs would be respected
by some individuals, but they would not deter vandals. In fact,
signs, which are visible from a distance, could draw attention to
a colony.
In order to make signs more effective, they should include a
warning and an explanation of why trespassing is prohibited.
Buckley and Buckley (1978) suggest two tiers of signs, an
informational sign to be erected some distance from the colony,
and a warning sign closer to the colony.
26
3.7.2.2
Pamphlets
An illustrated pamphlet could be developed for distribution by
the districts. This pamphlet could provide general information
on the biology and distribution of herons and egrets,
conservation goals, the sensitivity of colonial birds to
disturbances.
3.7.2.3
News Releases and Advertisements
News releases or advertisements could be circulated to
newspapers and to publications of major naturalist, outdoor
recreation or sportsmen's groups prior to the breeding season.
This would be a good way of informing the public about the
sensitivity of nesting herons and other colonial nesters.
3.7.2.4
Educational Viewing Programs
The assistance of a scientific authority on colonial birds is an
essential prerequisite in evaluating and selecting any site to be
used for educational viewing purposes, and in determining
precise distances for boardwalks or viewing stations.
Educational programs can be developed that make use of certain
colonies for educational viewing purposes. Colonies selected
should be those in which the birds are habituated to the
presence of humans. Viewing should take place only during the
least sensitive times of the breeding season (Figs. 3 and 4).
Guidelines concerning buffer zones should be strictly observed,
and boardwalks or fenced nature trails should be constructed at
distances well beyond the minimum buffer zone of 300 metres
to control viewer traffic. Viewing points should be established
beyond the buffer, in natural clearings or on small rises. Trees
or shrubs should not be removed or thinned to facilitate
viewing.
Groups using the boardwalks or trails should be accompanied
by a guide whose job it would be to give an interpretive talk
and to ensure that visitors remained well away from the nesting
birds.
27
3.7.2.5
A/V Shows and Exhibits
An audio-visual presentation and exhibits describing the
biology of herons and egrets, conservation goals, the sensitivity
of colonial birds, etc., could be developed as interpretiveeducational tools to be used at wildlife viewing weekends and in
provincial parks.
3.7.2.6
Local Interest Groups
Naturalists, hunters and other recreationalists can effectively
promote conservation interests in the community. If concern
exists about disturbances in a particular colony (or group of
colonies) these individuals should be notified, and an effort
made to obtain their assistance in policing the colony(ies) and
initiating protective measures. Contact with members of the
community may alert Ministry staff to potential problems.
4.0
Appendices
4.1
Census Instructions for Heronries
4.1.1
Terms Defining Status of Nests
Active Nests: those nests which are being used by breeding birds, and
which are distinguished by the presence of one or more of the following:
-
adults on the nest
-
eggs or young in the nest
-
"white-washing" (excrement) on the nest, tree branches or branches, or
or ground below the nest (see also definition for nests of unknown
status)
-
large blue egg shells, dead chicks, or food items on the ground.
Inactive Nests: those nests that lack any of the characteristics defining
active nests.
Nests of Unknown Status: those nests whose status is difficult to
determine because of visual barriers, or the presence of whitewash that
could be attributable to an active nest higher up on the same tree.
28
4.1.2
Censusing of Great Blue Heron Colonies in Woodlots and Swamps
The Ontario Heronry Inventory method used for censusing great blue
heron colonies in woodlots and swamps is as follows:
i
Each tree in the colony is marked with surveyor's tape after the
number of active nests, inactive nests or nests of unknown status
have been noted on the field sheet.
ii
Binoculars should be used to determine the status of nests.
Nest status should not be judged on the basis of size
considerations, since new nests can be extremely flimsy.
4.1.3
iii
Censusers should leave the colony immediately if young fall
fall from the nest or if predators such as crows, ravens or gulls
begin disrupting the colony.
iv
A check is made to ensure that all nest trees are marked and that
all field sheets are complete.
v
The surveyor's tape is removed and the censusers leave the colony.
Great Blue Heron Colonies in Deep Beaver Ponds
This procedure should be used if nest trees cannot be approached owing to
deep water, and if nests are visible from points along the "shore". It
should not be used if a view of the nests is obscured by dense foliage.
i
The colony should be divided into groups of nests using visual
reference points agreeable to the two individuals who will perform
the census.
ii
The number of nests in each grouping should be counted and
recounted by the two observers until both arrive at the same
number.
iii
The occupancy status of nests in each section should be agreed
upon (eg., active, inactive, or unknown).
iv
The above procedure should be repeated, using different vantage
points, if possible.
29
4.1.4
Colonies With Species Nesting Close to Ground
Caution must be used when censusing colonies in which the birds are
nesting close to the ground (eg., in low shrubs), since the potential for
disturbance is greater. The procedure described for woodlots and swamps
could be used by experienced personnel in small colonies. Ground transect
sampling or aerial censusing should be considered in large colonies to avoid
disturbing the birds for long periods of time.
30
4.2
Ontario Heronry Inventory Census Field Sheets and Record Sheets
Colony Number ______
ONTARIO HERONRY INVENTORY
GREAT BLUE HERON CENSUS: FIELD SHEET
Date of Census: ____________________
(month, day, year)
Time of Day: ____________ to ____________
(start)
(end)
Name(s) of censuser(s): _________________________________________________________
_____________________________________________________________________________
Colony name or location _________________________________________________________
_____________________________________________________________________________
Record the number of nests in each tree in the appropriate column: eg., 5 nests total; 3 active, 2
inactive. There should be a few "unknowns". If you cannot complete the count, at least try to
get as accurate an estimate as possible of the total number of nests present.
Total nests in tree
No. of active nests
(adults, eggs or young
present,
whitewashing visible)
No. of inactive nests
(No adults, eggs,
young or
whitewashing)
Please complete back of sheet before leaving colony
No. nests of
unknown status
31
Total nests in tree
No. of active nests
No. of inactive nests
No. of nests of
unknown status
Indicate type of supporting trees: deciduous _________ coniferous _________mixed _________
alive _________ dead _________ mixed _________ species (if known) ____________________
Estimated average height of nests from ground: _______________________________________
Wet ________
or dry ________ under nest trees (check one).
General conditions during census (approximate temperature, precipitation):
_____________________________________________________________________________
_____________________________________________________________________________
32
Colony Number ______
ONTARIO HERONRY INVENTORY
GREAT BLUE HERON CENSUS: RECORD SHEET
Complete as soon as possible after your census, and mail by July 15, 1981 to: OHI, Long Point
Bird Observatory, P. O. Box 160, Port Rowan, ON NOE 1MO
1.
Name and address of chief censuser:___________________________________________
________________________________________________________________________
2.
Colony name and location: (include military grid if possible) _______________________
________________________________________________________________________
3.
Date of Census: _______________________ Time of day: __________ to __________
(month, day, year)
(start)
(end)
4.
Weather conditions during census (approximate temperature, amount of precipitation):
________________________________________________________________________
5.
Census results:
Active
nests
Inactive
nests
Status
Unknown
Total
No. of nests:
Are the above totals actual counts __________ or an estimate ___________ (check one).
If the count was incomplete, give the reason below:
________________________________________________________________________
________________________________________________________________________
If more than one census was done, record the most reliable here, and give the results of
other censuses on the back of this sheet.
Was it easy ______ or difficult ______ to get a complete count of the nests in this
colony? (check one) If difficult, give reasons:
________________________________________________________________________
33
6.
Total no. nest trees: ______________________________________________________
7.
Tree type supporting nests (check one): deciduous _____ coniferous _____ both ______
8.
Status of nest trees (check one): alive __________ dead __________ both ___________
9.
Species of nest trees (if known): _____________________________________________
10.
Estimated average height of nests above ground: ________________________________
11.
Condition of heronry terrain (check appropriate space for each):
12.
Easy ________
or
difficult ________
to find heronry and way home.
Easy ________
or
difficult ________
to walk through heronry.
Wet ________
or
dry
under nest trees..
________
Were the directions provided adequate for you to find the colony? If not, explain why
and forward amended sketch map and/or written instructions, (including military grid
coordinates if possible) for future censusers.
________________________________________________________________________
________________________________________________________________________
13.
Was there any evidence during your census visit of threats to the future of this heronry?
(give details): ____________________________________________________________
________________________________________________________________________
14.
Please comment on the census methods and instructions, for the benefit of future
censusers. Were the instructions and record sheets clear and straightforward?
Yes ______ No ______ Please describe specific difficulties and make suggestions or
changes.
THANK YOU FOR YOUR HELP!
34
4.3
Forest Management Plans
A general knowledge of planning procedures is required if resource managers are to
ensure that fish and wildlife habitat requirements are considered in proposals for
various activities or developments. This section provides, as an example, a
description of the planning process for one activity - timber harvesting.
In order to effectively identify fish and wildlife concerns at the planning stage of
forest management units, Fish and Wildlife mangers must first be aware of the various
steps in the planning process. The steps outlined below are summarized from pages
two (2) and three (3) of "Standards and Guidelines for Moose Habitat Management in
Ontario" by the Ontario Moose Council.
The first planning step for all forestry management units entails the preparation of a
Management Plan Report. These reports are prepared either by the licenced holder of
an area large enough for "sustained yield management" or by the Ministry of Natural
Resources, in the case of all other units. Plans must be prepared in accordance with
specifications outlined in the "Manual of Management Plan Requirements for the
Province of Ontario" (January, 1976).
The specifications in the "Manual" provide for the identification of fish and wildlife
habitat requirements in Management Plan Reports. Section B(12) entitled "Other
Forest Uses", in Part 1 of the "Manual" states:
The requirements for forest uses other than timber production, such as fish and
wildlife production, recreation, wilderness, research and others are stated in this
section and are based on the capability of the area to provide them and the feasibility
of making them available.
Where plans for other uses on the area have been developed, a summary of each shall
be shown in this section; the original document shall be filed with the management
unit or may be appended to the plan.
In each particular case, a statement shall be made in this section as to how the
objectives for the other uses will be attained, by what means and with whose
cooperation. The agreed upon objectives shall be stated in Section 7 and shall also
form an integral part of the prescriptions made for silvicultural systems in Section 9.
Details of the requirement treatment shall be shown in the operating plan.
Concerns with respect to heronries must be identified in Management Plan Reports.
This ensures their consideration at the next stage of the planning process - The
Operating Plan.
35
The Operating Plan is worked out for a five (5) or ten (10) year period and outlines
specifications for actual work to be done in the management unit, such as cutting,
planting, etc. Any work to be undertaken must meet the standards described in the
Management Plan Report. The details of fish and wildlife habitat requirements must
be identified at this stage. In the case of heronries, buffer zone requirements, etc.,
would be identified.
Annual plans, as the name suggests, are prepared annually, and describe work to be
undertaken in any given management unit over a period of only twelve (12) months.
These plans further refine the work specifications outlined in the Operating Plan and
provide the last opportunity for change before final approval is given.
4.4
Buffer Zones Recommended by Colonial Bird Authorities
The recommendations of several colonial bird authorities on the buffer zone
requirements of heronries are presented as follows:
i
Buckley and Buckley (1978:28) in "Guidelines for the Protection and
Management of Colonially Nesting Waterbirds" advise that a 300 metre (1000
foot) buffer is suitable for most ground-nesting colonial birds, but recommend
"...an exceptionally wide buffer zone around the base of tall-tree colonies, as
the greater visibility from these heights renders them disturbable at greater
distances."
ii
Vermeer (letter dated September 17, 1977) recommends a no-boating buffer
zone of one kilometre (3,278.9 feet) for colonies situated on lake islands or
lakeshores.
iii
McVaugh (letter dated September 26, 1977) recommends "a minimum zone of
one-half mile (805 metres) radius... around all heronries."
The Fish and Wildlife Division of Alberta's Department of Recreation, Parks and
Wildlife has recently developed a draft "Colonial Waterbird Management Plan" for
white pelicans (Pelecanus erythrorhynchos), double-crested cormorants
(Phalacrocorax auritus) and great blue herons (Ardea herodius). The "Plan" proposes
that on Alberta Crown lands, all active great blue heron colonies and a half (0.5)
kilometre buffer strip should be designated as "Wildlife Protection Areas" under the
Wildlife Act. The acquisition of private lands supporting well-established heronries is
also recommended. In each case, the property to be acquired would include the colony
site and a minimum half (0.5) kilometre (1640.5 foot) buffer zone; ideally, the quarter
(.25) section in which the colony is situated would be purchased. If a landowner is
unwilling to sell, an attempt will be made to negotiate an agreement for the protection
of the colony and the habitat in a minimum half (0.5) kilometre buffer zone.
36
5.0
Selected References
Adams, A. M.; J. Bunn; B. S. Davis; A. L. Jones; L. W. Odreg., 1973. A study of the Pig's Eye
Lake heron colonies. The Loon 45(2):32-45.
Bent, A. C. 1963. Life histories of North American marsh birds. Dover Publications Inc., New
York. 392 pp.
Bjorklund, R. G. 1975. On the death of a midwestern heronry. The Wilson Bulletin 87(2):284287.
Blaker, D. 1969. Behaviour of the cattle egret Ardeola ibis. Ostrich 40(3):75-129.
Buckley, P. A., and F. G. Buckley. 1978. Guidelines for the protection and management of
colonially nesting waterbirds. North Atlantic Regional Office, National Park Service,
Boston, Massachusetts 02109. 54 pp.
Burger, J. 1981. Effects of human disturbance on colonial species, particularly gulls. Colonial
Waterbirds 4:28-36.
(
) The effect of human activity on birds at a coastal bay. Biological Conservation
21:231-241.
Cottrille, W. P., and B. D. Cottrille. 1958. Great blue heron: behaviour at the nest.
Miscellaneous Publication No. 102, Museum of Zoology, University of Michigan.
15 pp.
Custer, T. W.; R. G. Osborn; and W. F. Stout. 1980. Distribution, species abundance and
nesting site use of Atlantic coast colonies of herons and their allies. The Auk 97:591600.
Dunn, E.; J. Siderius; and D. Hussell. 1981. A census of great blue herons in Ontario:
1980 and 1981. Long Point Bird Observatory. Unpublished report. 74 pp.
Godfrey, E. W. 1966. The birds of Canada. National Museums of Canada Bulletin No. 203,
Biological Series No. 73. 428 pp.
Goering, D. K., and R. Cherry. 1971. Nestling mortality in a Texas heronry. Wilson Bulletin
83(3):303-305.
37
Gray, P. A. 1978. The distribution and abundance of the great blue heron (Ardea herodias) in
the West Patricia Planning Area, 1978. West Patricia Land Use Plan. Wildlife Technical
Report No. 9. 28 pp.
Hagey, B. n.d. Life in a heronry in great blue heronries in the Grand River watershed.
Compiled by C. A. Campbell and C. C. Coumans for the Conservation Committee of the
Kitchener-Waterloo Field Naturalists.
Henney, C. J. 1978. Great blue herons respond to nesting habitat loss. Wildlife Society
Bulletin 6(1):35-37.
Jenni, D. A. 1969. A study of the ecology of four species of herons during the breeding season
at Lake Alice, Alachua County, Florida. Ecological Monographs 39(3):245-270.
Kushlan, J. A. 1979. Effects of helicopter censuses on wading bird colonies. Journal of Wildlife
Management 43(3):756-760.
Markham, B. J. and S. H. Brechtel. 1978. Status and management of three colonial waterbird
species in Alberta. Proceedings of the Colonial Waterbird Group, 1978:55-64.
McVaugh, Jr., W. 1972. The development of four North American herons. The Living Bird.
Eleventh Annual of the Cornell Laboratory of Ornithology. Cornell University, Ithaca,
New York, 155-173.
Meyerriecks, A. J. 1960. Comparative breeding behaviour of four species of North American
herons. Publications of the Nuttal Ornithological Club No. 2. Published by the Club.
Cambridge, Massachusetts.
Mock, D. M. 1978. Repertoire shifts and extra-marital courtship in herons. Behaviour 69:5671.
Pratt, H. M. 1970. Breeding biology of great blue herons and common egrets in central
California. The Condor 72:407-416.
(
). 1972. Nesting success of great blue herons and common egrets at
Audubon Canyon Ranch in 1971. American Birds 26(4):699-702.
(
). 1974. Breeding of great blue herons and great egrets at Audubon
Canyon Ranch, California, 1972-1973. Western Birds 5:127-136.
Siegfried, W. R. 1972. Breeding success and reproductive output of the cattle egret. Ostrich
43:43-55.
38
Simpson, K. and J. P. Kelsall. 1978. Capture and banding of adult great blue herons at Pender
Harbour, British Columbia. Proceedings of the Colonial Waterbird Group, 1978:71-78.
Teal, J. M. 1965. Nesting success of egrets and herons in Georgia. Wilson Bulletin 77(3):257263.
Thompson, D. H. 1977. Declines in populations of colonial waterbirds nesting within the
floodplain of the upper Mississippi River. Proceedings of the Colonial Waterbird Group,
1977:26-37.
Tremblay, J., and L. N. Ellison. 1976. Reproductive success of the black-crowned night heron in
the St. Lawrence estuary in 1975 and 1976. Preliminary text of study funded by National
Research Council and Canadian Wildlife Service.
(
). 1979. Effects of human disturbance on breeding of black-crowned night
herons. The Auk 96:364-369.
(
). 1980. Breeding success of the black-crowned night heron in the St.
Lawrence estuary. Canadian Journal of Zoology 58:1259-1263.
Vermeer, K. 1970. Insular great blue heron colonies on large Manitoba Lakes. The Blue Jay
28(2):84-86.
Werschkul, D., E. McMahon, and M. Leitschuh. 1976. Some effects of human activities on the
great blue heron in Oregon. Wilson Bulletin 88:660-662.
Werschkul, D., E. McMahon, M. Leitschuh, S. English, C. Skibinski, and G. Williamson. 1977.
Observations on the reproductive ecology of the great blue heron (Ardea herodias) in
western Oregon. The Murrelet 58:7-12.
Wiese, J. H., and T. Smith-Kenneally. 1977. A heron colony called Pea Patch. Delaware
Conservationist 21(2):8-15.
Wolford, J. W. 1966. An ecological study of the black-crowned night heron in southern Alberta.
Unpublished M.Sc. Thesis, University of Alberta, 1966. 60 pp.
Wolford, J. W., and D. A. Boag. 1971. Distribution and biology of black-crowned night herons
in Alberta. Canadian Field Naturalist 85(1):13-19